The technical field of the invention relates to the transmission of two DSL (Digital Subscriber Line) services via a common subscriber access line between a subscriber terminal device and a subscriber switching center.
According to the prior art, the two DSL services which are transmitted via a common subscriber access line are essentially an ISDN service and an ADSL service.
According to the respective standards for ISDN and ADSL, the ISDN band (0-80 kHz) and the ADSL band (20 kHz to 1.1 MHz) overlap. If, for example, a subscriber terminal device is transmitting both an ISDN signal and an ADSL signal, the two signals must be separated from one another on the line using the out-of-band method.
U.S. Pat. No. 5,742,527 describes a flexible ADSL receiver (ADSL=Asymmetrical Digital Subscriber Line). In this known ADSL receiver, the bandwidth up to 138 kHz is reserved for ISDN transmission (ISDN=Integrated Service Digital Network), and the upstream channel of the ADSL starts from 138 kHz, with the downstream channel being specifically shifted.
In the recent past, various options have been implemented to allow ADSL data to be transmitted in parallel with ISDN data. All of these known proposals have required two transceivers, to be precise in each case one for the ISDN data and a further one for the ADSL data, with a specific frequency band being reserved for each modulation scheme, provided by the respective transceiver.
FIG. 1 shows a schematic arrangement for transmission of ISDN data and ADSL data via a common subscriber access line from a subscriber terminal device to a subscriber switching center, and from a subscriber switching center to a subscriber terminal device. The arrangement shown in FIG. 1 has a subscriber terminal device TEE which is connected to a subscriber switching center TVS via a common subscriber access line TAL. Furthermore, the subscriber switching center TVS is connected firstly to a postal private branch exchange PSTN for further transmission of speech data, and to a data network DN for further transmission of data.
The subscriber terminal device TEE has an analog splitter S, which separates the frequencies of the ISDN signal and of the ADSL signal, passes the ISDN signal to an ISDN transceiver ISDN-T, and passes the ADSL signal to an ADSL transceiver ADSL-T. The ISDN transceiver ISDN-T modulates and demodulates the data to be transmitted and the data to be received, respectively. ISDN data which is applied to the subscriber access line TAL is passed from the splitter S to the ISDN transceiver ISDN-T depending on its frequency, the ISDN transceiver ISDN-T demodulates this data, and sends the demodulated data to the ISDN terminal device ISDN-E. If, in contrast, the ISDN terminal device ISDN-E is generating data, then this is transmitted to the ISDN transceiver ISDN-T, which modulates this data and sends it via the splitter S and the subscriber access line TAL to the subscriber switching center TVS. The data path of the ADSL data operates in an analogous manner via the splitter S, via the ADSL transceiver ADSL-T and the ADSL terminal device ADSL-E, for example a computer.
The subscriber switching center TVS has an ISDN central office ISDN-ZB and an ADSL central office ADSL-ZB. The two central offices are connected to the subscriber access line TAL by means of an analog splitter S. A data path for ISDN data and a data path ADSL data are thus provided in the subscriber switching center TVS as well. The analog splitter S in the subscriber switching center TVS essentially has the same task as the splitter S in the subscriber terminal device TEE. Data received from the subscriber access line TAL is separated by the splitter S in the subscriber switching center TVS such that ISDN data from a lower frequency band is transmitted to or received from the ISDN central office ISDN-ZB, and higher-frequency components of the ADSL band are transmitted to or received from the splitter S to the ADSL central office ADSL-ZB.
The ISDN central office ISDN-ZB has an ISDN transceiver ISDN-T for each subscriber access line TAL which is connected to the subscriber switching center TVS. ISDN data received from the subscriber switching center TVS is processed by the appropriate ISDN transceiver ISDN-T with respect to the subscriber terminal device TEE from which the data was passed, and is passed to the postal private branch exchange PSTN.
An ADSL transceiver ADSL-T is likewise available in the ADSL central office ADSL-ZB for each subscriber terminal device TEE which is connected via a dedicated subscriber access line TAL, demodulates the received data and makes it available to a connected data network DN. When data is being transmitted in the complementary case from the data network DN to the subscriber terminal device TEE, the data network DN makes this data available, in a first step, to the corresponding ADSL receiver, ADSL-T. This modulates this data onto an ADSL band, and transmits this by means of the splitter S in the subscriber switching center TVS via the subscriber access line TAL to the corresponding subscriber terminal device TEE. The splitter S in the subscriber terminal device TEE then separates the frequency of the ADSL data signal from other frequencies, and makes it available to the ADSL transceiver ADSL-T in the subscriber terminal device TEE. The ADSL transceiver ADSL-T demodulates the ADSL data, and makes the demodulated ADSL data available to the ADSL terminal device ADSL-E.
The disadvantages of the prior art for transmission of hybrid DSL data via a common subscriber access line TAL are as follows: the two DSL services, essentially ISDN and ADSL according to the prior art, have different transmission ranges with respect to their transmission power. In this case, the DSL service ISDN, with the greater range, has unused reserves, that is to say the transmission power is not matched to the transmission channel and is accordingly unnecessarily high. An inadequate or unnecessarily high transmission power results in an unnecessarily high interference load for the remaining systems and for its own subscriber access line TAL. An unnecessarily high interference load means that the data rate which is transmitted via the subscriber access line TAL or via the subscriber access lines TAL must be reduced in order to achieve redundancy on the line. In a corresponding manner, an unnecessarily high transmission power on a subscriber access line TAL means an unnecessary reduction in the data transmission rate on the subscriber access line TAL and on all the other subscriber access lines TAL located in the same bundle.
A further disadvantage of the prior art is that the splitters S which are used in the subscriber terminal device TEE and in the subscriber switching center TVS are analog low-pass filters. Analog low-pass filters occupy a large amount of space and are not consistent with a high packing density, particularly in the subscriber switching centers TVS.
The object of the present invention is to provide a hybrid DSL system for transmission of hybrid DSL data via a subscriber access line TAL, with an unnecessarily high interference load on the subscriber access line TAL being reduced, and with the overall data transmission rate on the subscriber access line TAL thus being maximized.
According to the invention, this object is achieved by the hybrid DSL system specified in claim 1 and by the method specified in claim 33 for transmission of hybrid DSL data via a subscriber access line.
The hybrid DSL system according to the invention and the corresponding method for common transmission of hybrid DSL data via a common subscriber access line have the advantage over the known solution approaches that the two transceivers for transmission of the hybrid DSL data are connected via a data link for interchanging parameters. Parameters are interchanged via this data link between the first DSL transceiver and the second DSL transceiver in order, inter alia, to adequately match the transmission powers of the two transceivers, and thus to increase the overall data transmission rate of both transceivers.
The idea on which the present invention is based essentially comprises the two DSL transceivers being provided with a data link for interchanging parameters.
According to the invention, a hybrid DSL system for transmission of hybrid DSL data via a subscriber access line is provided for this purpose, with a baseband transceiver being provided for transmission of first data in a base frequency band via the subscriber access line at a first data transmission rate, a non-baseband transceiver being provided for transmission of second data in a non-base frequency band via the subscriber access line at a second data transmission rate, and a data link being provided for interchanging parameters between the baseband transceiver and the non-baseband transceiver in order to increase the overall data transmission rate of both transceivers.
Advantageous developments and improvements of the respective subject matter of the invention can be found in the dependent claims.
According to one preferred development of the invention, the first data which is intended to be transmitted from the hybrid DSL system is speech data.
According to a further preferred development, the overall data transmission rate is the sum of the first data transmission rate and of the second data transmission rate.
According to a further preferred development, the baseband transceiver and the non-baseband transceiver are connected to a controller.
One advantage of this arrangement, according to which the baseband transceiver and the non-baseband transceiver are connected to a controller, is that the controller allows both the baseband transceiver and the non-baseband transceiver to be adjusted such that, for example, parameters such as the transmission power can be adequately matched.
According to a further preferred development, the baseband transceiver, the non-baseband transceiver and the controller form a control loop.
One advantage of this development is that the adequate matching of the parameters for the baseband transceiver and for the non-baseband transceiver is matched in a controlled manner.
According to a further preferred development, the data link for interchanging parameters is formed by a connection from the baseband transceiver to the controller, and by a connection from the non-baseband transceiver to the controller.
One advantage of this development is that the formation of the data link via the baseband transceiver, the non-baseband transceiver and the controller means that there is no need to provide a dedicated data link between the baseband transceiver and the non-baseband transceiver.
According to a further preferred development, the baseband transceiver and the non-baseband transceiver are integrated. One advantage of this development is that the integration of the baseband transceiver and of the non-baseband transceiver saves space.
According to a further preferred development of the invention, the baseband transceiver, the non-baseband transceiver and the controller are integrated.
According to a further preferred development of the invention, the subscriber access line is intended for the transmission of hybrid DSL data in a bundle of two or more subscriber access lines for transmission of at least one data stream.
According to a further preferred development, the data link is provided by an interface between the baseband transceiver and the non-baseband transceiver.
According to a further preferred development, the data link is a serial interface between the two transceivers.
According to a further preferred development, the data link is a parallel interface between the two transceivers.
According to a further preferred development, the transmission power of the baseband transceiver is adjustable so as to reduce the interference load for the subscriber access line for transmission of hybrid DSL data.
According to a further preferred development, the transmission power of the baseband transceiver (101) is adjustable so as to increase the second data transmission rate of the non-baseband transceiver (102).
One advantage of this development is that the adjustment of the transmission power of the baseband transceiver increases the second data transmission rate of the non-baseband transceiver, thus increasing the overall data transmission rate of the hybrid DSL system.
According to a further preferred development, the transmission power of the baseband transceiver is adjustable so as to reduce an interference load for the bundle of two or more subscriber access lines for transmission of at least one data stream.
One advantage of this development is that the adjustment of the transmission power of the baseband transceiver also reduces the interference load for other subscriber access lines within the bundle, so that the data transmission rate of the other subscriber access lines is increased.
According to a further preferred embodiment, the transmission power of the non-baseband transceiver is adjustable so as to reduce the interference load for the subscriber access line for transmission of the hybrid DSL data.
One advantage of this development is that the reduction in the interference load for the subscriber access line increases the overall data transmission rate of the subscriber access line.
According to a further preferred development, the transmission power of the non-baseband transceiver is adjustable so that an increase in the first data transmission rate of the baseband transceiver is provided.
One advantage of this development is that increasing the first data transmission rate of the baseband transceiver increases the overall data transmission rate of the subscriber access line or of the subscriber access lines.
According to a further preferred development, the transmission power of the non-baseband transceiver is adjustable so as to reduce the interference load for the bundle of two or more subscriber access lines for transmission of at least one data stream.
One advantage of this development is that the reduction in the interference load for the bundle of two or more subscriber access lines makes it possible to increase the respective data transmission types on these subscriber access lines.
According to a further preferred development, the baseband transceiver is an ISDN transceiver.
According to a further preferred development, the non-baseband transceiver is an XDSL transceiver.
According to a further preferred development, the XDSL transceiver is an ADSL transceiver.
According to a further preferred development, the XDSL transceiver is a VDSL transceiver.
According to a further preferred development, the parameters which are interchanged between the baseband transceiver and the non-baseband transceiver include both line parameters for the subscriber access lines and status parameters for the two transceivers.
According to a further preferred development, the line parameters include the channel attenuation on the subscriber access line, the signal-to-noise ratio on the subscriber access line, and interference parameters for the bundle of two or more subscriber access lines.
One advantage of this preferred development is that the stated parameters can be used for adjustment of the baseband transceiver and of the non-baseband transceiver, so that, for example, their transmission power is adequately matched.
According to a further preferred development, the status parameters include an activation state of the baseband transceiver, an activation state of the non-baseband transceiver, a block error rate for the baseband transceiver, a block error rate for the non-baseband transceiver, bandwidth setting parameters for the baseband transceiver, and bandwidth setting parameters for the non-baseband transceiver.
One advantage of this development is that the status parameters which are provided can be used for adjustment of the baseband transceiver and the non-baseband transceiver such that it is possible, for example, to adequately match their transmission power.
According to a further preferred development of the invention, a splitter, which is connected to the baseband transceiver and to the non-baseband transceiver, separates the base frequency band of the baseband transceiver and the non-base frequency band of the non-baseband transceiver.
According to a further preferred development, the splitter is a first-order filter system.
According to a further preferred development, the splitter is integrated.
According to a further preferred development of the invention, the splitter, the controller, the baseband transceiver and the non-baseband transceiver are integrated on a common assembly.
According to a further preferred development, the hybrid DSL system is provided in a subscriber terminal device.
According to a further preferred development, the hybrid DSL system is provided in a subscriber switching center.
According to a further preferred development, the hybrid DSL system is in each case provided in a subscriber terminal device and in a subscriber switching center, with the subscriber terminal device being connected to the subscriber switching center by means of a common subscriber access line.
Exemplary embodiments of the invention will be explained in more detail in the following description, and are illustrated in the drawings, in which: